(3x+6)+(x)=90

Solution for (3x+6)+(x)=90 equation:

Simplifying
(3x + 6) + (x) = 90

Reorder the terms:
(6 + 3x) + (x) = 90

Remove parenthesis around (6 + 3x)
6 + 3x + (x) = 90
6 + 3x + x = 90

Combine like terms: 3x + x = 4x
6 + 4x = 90

Solving
6 + 4x = 90

Solving for variable 'x'.

Move all terms containing x to the left, all other terms to the right.

Add '-6' to each side of the equation.
6 + -6 + 4x = 90 + -6

Combine like terms: 6 + -6 = 0
0 + 4x = 90 + -6
4x = 90 + -6

Combine like terms: 90 + -6 = 84
4x = 84

Divide each side by '4'.
x = 21

Simplifying
x = 21